We observed a total of 57 incidences of copulation in a colony of the Indian flying fox, Pteropus giganteus, over 13 months under natural conditions. The colony consisted of about 420 individuals, roosting in a Ficus religiosa tree. Copulations occurred between 07.00 h and 09.30 h from July to January, with more occurring in October and November. Initially males groomed their penis before approaching a nearby female. Females typically moved away and males followed. When the female stopped moving, the male started licking her vagina (cunnilingus). Typically each bout of cunnilingus lasted for about 50 s. In 57 out of 69 observations, the male mounted the female and copulated. The duration of copulation varied from 10 to 20 sec. After completion of copulation, the male continued cunnilingus for 94 to 188 sec. The duration of pre-copulatory cunnilingus and copulation was positively correlated whereas, the duration of pre- and post-copulatory cunnilingus was negatively correlated. Apart from humans, oral sex as foreplay prior to copulation is uncommon in mammals. Another pteropodid bat, Cynopterus sphinx exhibits fellatio with females licking the penis of males during copulation. It appears that bats, especially pteropodids perform oral sex, either cunnilingus or fellatio, possibly for achieving longer copulation.